Sensor elements and methods for operating the sensor elements for determining at least one concentration of a gas in a measuring gas chamber are known from the related art. Without limiting further possible embodiments, the present invention is described hereafter essentially with reference to methods and devices which are used to quantitatively and/or qualitatively detect at least one concentration of at least one gas component in the gas, in particular in a gas mixture. The gas mixture may be an exhaust gas of an internal combustion engine, for example, in particular in the automobile sector. The measuring gas chamber may be an exhaust system, for example. The sensor element may be a Lambda probe, for example. As an alternative, the sensor element may also be an NOx sensor. Lambda probes are described in Robert Bosch GmbH: Sensoren im Kraftfahrzeug [Sensors in the Motor Vehicle], 1st edition 2010, pages 160-165, for example. The gas component may in particular be oxygen and/or nitrogen and/or at least one nitrogen oxide and/or at least one hydrocarbon and/or another type of gas component. Sensor elements of the described type may in particular be based on the use of one or multiple solid electrolytes, i.e., on the use of solids, in particular ceramic solids, which have ion-conducting, in particular oxygen ion-conducting, properties. Examples of such solid electrolytes are zirconia-based solid electrolytes, such as yttria-stabilized zirconia (YSZ) and/or scandium-stabilized zirconia (ScSZ). Lambda probes generally operate according to the principle of a pump cell. The concentration of the gas may be an oxygen partial pressure and/or an oxygen concentration and/or a volume percent of oxygen. The usually linear correlation of a limit current with an oxygen partial pressure may be used, for example, to carry out a measurement of the oxygen partial pressure in the exhaust gas.
In the case of broadband lambda probes, also referred to as broadband lambda sensors, for example, a quantity of O2 or fat gas diffusing in a measuring cavity is measured either based on a limit current, which may be in single-cell sensors, in particular in the LSP (proportional lambda probe), or based on a pump current which is necessary to regulate a cavity concentration to lambda=1 and which may then also correspond to a limit current, for example in dual-cell sensors, in particular in the LSU (universal lambda probe). A flowing pump current, in particular in the form of a measuring current, is usually proportional to the O2 content in the exhaust gas and/or to the fat gas concentration in the exhaust gas.
A pump voltage necessary for electrochemical reactions and ohmic losses in the solid electrolyte is usually ensured by a so-called Nernst control in a dual-cell sensor. In a single-cell sensor, the pump voltage is usually adjusted to the pump current with the aid of a linear ramp or multiple ramps, for example having different slopes. This is referred to as pump voltage adjustment, for example.
The methods and devices from the related art are believed to have have several disadvantages. For example, a charge of a double layer capacitance of an inner pump electrode (IPE) is reversed in the case of the pump voltage adjustment for single-cell sensors. The resulting charge-reversal currents are usually observable as overshoots and/or undershoots in a probe signal, for example in the limit current, when the concentration of gas in the measuring gas chamber changes, for example in the case of changes in the exhaust gas composition, and result in signal errors, for example. When the changes of the gas in the measuring gas chamber are rapid, for example in the case of rapid gas exchanges, these signal errors may be particularly pronounced and may cause many applications which require high dynamics of the probe signal not to be operable, for example. A method and a device which at least to some extent mitigate the disadvantages known from the related art would therefore be desirable.